The preparation of isophorone by alkaline condensation of acetone at a high temperature and under pressure is well known. In addition to producing isophorone by alkaline condensation, the process produces certain secondary products as well. Some secondary products, such as mesityl oxide, may be easily eliminated by distillation. Other products, however, particularly those which are only slightly more volatile than isophorone, are separated only with difficulty, if at all. This is the case even using distilling columns with a high degree of separating power.
The presence of secondary products in industrial isophorone is particularly undesirable. Some secondary products have a strong yellow coloring which militates against the production of colorless commercial grade isophorne. Further, these secondary products accelerate a new progressive coloring of isophorone. Also, the secondary products may increase the acidity of stored isophorone by oxidation.
French Pat. No. 1,205,799 describes treating dry, colored isophorone with an aromatic sulfonic acid at a temperature falling between 80.degree. C. and 160.degree. C. The isophorone is then separated from the resulting mixture by distillation. This process has several drawbacks. The added sulfonic acid is wasted upon being eliminated with the distillation residues. Furthermore, the presence of sulfonic acid enhances the degradation of the isophorone during the treatment. Another disadvantage is the corrosion phenomena which is inevitable whenever steel is employed in the process.
French Pat. No. 1,215,326 describes a process for obtaining colorless isophorone by treating isophorone with fuller's earth, a natural product belonging to the group of aluminum silicates known as montmorillonites. As is the case with several natural products, the characteristics of fuller's earth are subject to variation. Accordingly it is dangerous to prepare an industrial product like isophorone with this unconstant auxiliary product.
Thus, a process which eliminates the problems and overcomes the disadvantages of the prior art as well as to obtain a stable colorless product is of great value.